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Platform Description

Defense Meteorological Satellite Program (DMSP) Satellite F8

Summary

The Defense Meteorological Satellite Program (DMSP) provides global visible
and infrared cloud data and other specialized meteorological, oceanographic
and solar-geophysical data in support of worldwide Department of Defense (DoD)
operations. The DMSP F8 satellite, launched in June 1987, is in a near circular,
sun synchronous, polar orbit. This document describes the DMSP mission, the
satellite, and its environment. The document also briefly describes the ground
data system. Separate platform description documents are available for the F10, F11, F13, F15, and F17 satellites.

DMSP, originally known as the Defense System Applications Program (DSAP) and the Defense Acquisition and Processing Program (DAPP), is a long-term USAF effort in space to monitor the meteorological, oceanographic and solar-geophysical environment of the Earth in support of DoD operations. All spacecraft launched have had a tactical (direct readout) and a strategic (stored data) capacity. In December 1972, DMSP data were declassified and made available to the civil and scientific communities. The USAF maintains an operational constellation of two near-polar, sun-synchronous satellites.

The DMSP program office is located at the Space Systems Division, Air Force Material Command, Los Angeles Air Force Station, Los Angeles, California 90009-2960. Funding is provided by the Department of Defense (DoD).

The DMSP mission is to provide global visible and infrared cloud data and other specialized
meteorological, oceanographic and solar-geophysical data in support of worldwide Department
of Defense (DoD) operations.

DMSP Satellite F8 was built by General Electric's Astro-Space Division (now part of Martin
Marietta Astro Space). It was launched on June 19, 1987 from Vandenberg AFB, California
using an Atlas E rocket. The spacecraft is 3.5 meters in length with a diameter of 1.2 meters
with an on-orbit mass of 725 kilograms. It has a design lifetime of 30 months. Power is
provided though a 9.29 sq-m solar cell panel. Attitude is controlled using momentum wheels
and magnetic coils using a strap-down star sensor and gyros as the reference.

Short-term changes in attitude are measured using three orthogonal gyroscopes. A strap down
star sensor is used to bound the effects of gyroscope drift. The desired attitude is computed
based upon a star catalog and an ephemeris table uplinked to the spacecraft daily. Three-axis
attitude control is maintained in the orbital configuration by automatic momentum exchange
between three momentum wheels. Onboard magnetic coils provide controlled interaction with
the Earth's magnetic field to prevent the accumulation of wheel secular momentum. Operations
of these coils is under control of the closed loop spacecraft attitude control system. Both the
momentum wheels and gyroscopes are backed up by a fourth skewed unit for redundancy.

Data are transmitted in real time to tactical terminals worldwide. Data are also stored using onboard recorders for transmission to and processing by the Air Force Global Weather Central (AFGWC), Offutt AFB, Nebraska and the Fleet Numerical Meteorology and Oceanography Center (FNMOC), Monterey, California. Both AFGWC and FNMOC relay the SSM/I, SSM/T and SSM/T2 data to the National Environmental Satellite, Data, and Information System (NESDIS). AFGWC also sends the entire data stream to the National Geophysical Data Center (NGDC).

Data are transmitted in real time to tactical terminals worldwide. Data are also stored using onboard recorders for transmission to and processing by the Air Force Global Weather Central (AFGWC), Offutt AFB, Nebraska and the Fleet Numerical Meteorology and Oceanography Center (FNMOC), Monterey, California. Both AFGWC and FNMOC relay the SSM/I, SSM/T and SSM/T2 data to the National Environmental Satellite, Data, and Information System (NESDIS). AFGWC also sends the entire data stream to the National Geophysical Data Center (NGDC).

OLS: The Operational Linescan System (OLS) measures visible (0.4-1.1 micrometers) and infrared (10.25-12.6 micrometers) wavelengths to provide day and night cloud cover imagery. The satellite measures data at a 0.56 km resolution, which is averaged on board, to produce global coverage at 2.7 km resolution. All of the 2.7 km resolution (smooth) data are downlinked to the ground sites while a small amount of the 0.56 km resolution (fine) data is stored and downlinked. The OLS is the primary sensor on each DMSP satellite.

SSM/T-1: Special Sensor Microwave Temperature Sounder. The SSM/T is a seven channel, cross track nadir scanning passive microwave sounder having a field of view of 14.4 degrees. It measures the Earth surface and atmospheric emission in the 50 to 60 GHz oxygen band. At nominal altitude, the subtrack spatial resolution is an circle of 174 km at nadir and an ellipse of 213x304 km toward the limb. There are seven total cross-track scan positions separated by 12 degrees at frequencies 50.5, 53.2, 54.35, 54.9, 58.4, 58.825 and 59.4 GHz.

SSJ/4: Precipitating Plasma Monitor. The SSJ/4 measures the transfer energy, mass, and momentum through the magnetosphere-ionosphere in the Earth's magnetic field. The SSJ/4 sensor consists of four electrostatic analyzers that record the flux of precipitating ions or electrons at 20 fixed energy channels between 50 eV and 30 keV.

SSIES: Special Sensor Ionospheric Plasma Drift/Scintillation Meter. The SSIES measures the ambient electron density and temperatures, ambient ion density, the average ion temperature and molecular weight, the plasma drift and scintillation at the DMSP orbital altitude.

SSB/X-M: Gamma Ray Particle Detector. The SSB/X-M is an array-based system that detects the location, intensity, and spectrum of X-rays emitted from the Earth's atmosphere.